In a contact-type measuring method to measure the contour shape or the surface roughness of a workpiece by allowing a probe to make contact with the workpiece, for example, shapes as shown in FIGS. 10A-10D as the tip shape of a probe are known. Of these, with respect to further highly precise measurement in submicron dimensions or less, the tip shape of a probe is basically a spherical shape as shown in FIG. 10A or FIG. 10B so as to prevent an error caused by the tip shape as much as possible. Especially, the shape as shown in FIG. 10A can be highly precisely produced with ease, being most precise in the contact-type measuring method in submicron dimensions or less, resulting in a mainstream shape.
As the contact-type measuring method, a method is known in which a probe as described above is brought into contact with a workpiece and then the point contact position with the workpiece is extracted based on data calculated by offsetting a known probe shape portion from the central coordinate of the probe possessed by the measuring device to capture a shape. When the tip is spherical, extraction is carried out using data calculated by offsetting a known R from the tip spherical center of the probe.
For example, Patent Documents 1 and 2 describe techniques with respect to shape measurement using a spherical stylus, and Patent Document 3 describes a technique for shape measurement using a probe having a spherical face as the tip face shape and a taper face formed so as to smoothly lead to the spherical face in the outer circumference thereof.